CN105363473A - Low-carbon olefin platinum catalyst made through dehydrogenation of low-carbon alkane - Google Patents

Abstract

The invention relates to a low-carbon alkane dehydrogenation platinum catalyst and a preparation method thereof, which mainly solves the problems of low conversion rate of the catalyst and decreased selectivity during use in the prior preparation technology. In the present invention, transition metal elements such as copper, nickel, manganese, and cobalt are firstly introduced into the zinc ferrite carrier by co-precipitation method to obtain a composite metal oxide carrier, and then the platinum component is loaded by impregnation method, that is, the aqueous solution of soluble platinum impregnated salt , the platinum catalyst is obtained after drying, roasting and water vapor treatment. By using propane/isobutane as raw material, at a reaction temperature of 520-620°C, a reaction pressure of 0-0.4MPa, an alkane mass space velocity of 0.1-8.0h ^-1 , and a volume ratio of H ₂ O/C _n H _2n+2 of 1 Under ~18 conditions, the raw material is contacted with the catalyst to generate propylene/isobutene, which solves this problem well and can be used in the industrial preparation of catalysts for the dehydrogenation of light alkanes to light olefins.

Description

Platinum catalyst for the dehydrogenation of low-carbon alkanes to low-carbon olefins

technical field

The invention relates to a platinum catalyst used for dehydrogenating low-carbon alkanes to produce low-carbon olefins.

Background technique

Propylene/isobutylene mainly comes from the co-production or by-product of steam cracking and fluid catalytic cracking in refineries, and can be widely used in the synthesis of polymers, gasoline additives, rubber and various chemical intermediates. With the increasing demand for low-carbon olefins, the traditional production process is difficult to meet the rapid growth of market demand. A large amount of low-carbon alkanes obtained from refineries are the main components of liquefied petroleum gas, which are mainly used as civil fuels. The development of the process of producing low-carbon alkenes from low-carbon alkanes is of great significance for making full use of low-carbon alkanes to open up new sources of alkenes. At present, the alkane catalytic dehydrogenation technology is represented by the Oleflex process of UOP Company and the Catofin process of Lummus Company. There is no production device for dehydrogenating low-carbon alkanes to low-carbon olefins in China.

The catalytic reaction of dehydrogenation of low-carbon alkanes is carried out under high temperature and low pressure conditions, and the catalyst is severely deactivated by carbon deposition. The development of catalysts with high activity, high selectivity and high stability has become the key to this technology. The catalyst disclosed in Chinese patent (CN200710025372.X) is a preparation method in which alumina-modified mesoporous molecular sieves are impregnated with platinum-tin components on the carrier, the conversion rate of propane is only 17%, and the selectivity of propylene is 93%; Chinese patent (CN200710023431 .X) adopt the hydrothermal synthesis method to introduce tin into the ZSM-5 molecular sieve carrier, and use the impregnation method to support the platinum component. After the catalyst runs for 100 hours, the propane conversion rate is higher than 30%, and the propylene selectivity is 99%, but the The patent does not provide stability data for the charcoal regeneration process. Chinese patents (CN200710020064.8) and (CN200710133324.2) disclose a platinum-tin catalyst for propane dehydrogenation reaction, which adopts the preparation method of co-impregnation of tin component and platinum component, and the carrier is Y type, ZSM-5 After 720 hours of continuous operation of the catalyst containing Na-containing molecular sieves, the conversion rate of propane was 30.5%, and the selectivity of propylene was 96.4%, but the activity decreased by half after two charcoal regenerations. The U.S. patent discloses the aluminate carrier Pt catalyst (US3957688; US4041099; US5073662) that adopts the Pt catalyst (US5430220) that zinc aluminate spinel is a carrier and the auxiliary agents such as Au, Ag to promote, and catalyst all exists conversion efficiency low, in The problem of selectivity decline during use.

The above-mentioned catalysts all use alumina or aluminate to support the active components of the catalyst. The activity of the catalyst is not high during high-temperature use or after charcoal regeneration, and the selectivity gradually decreases during operation. There is no report on the use of a new type of composite ferrite carrier for the preparation of platinum-tin catalysts for the dehydrogenation of low-carbon alkanes to low-carbon olefins.

Contents of the invention

One of the technical problems to be solved by the present invention is the problem that the existing catalysts have low activity during high temperature use or after regeneration by burning charcoal, and the selectivity gradually decreases during operation. Provided is a new low-carbon alkane dehydrogenation platinum catalyst, which is used in the process of low-carbon alkane dehydrogenation to low-carbon olefins, and has the advantages of high catalyst conversion rate and stable selectivity under high temperature and charcoal regeneration conditions. The second technical problem to be solved by the present invention is to provide a catalyst preparation method corresponding to one of the technical problems to be solved.

In order to solve one of the above-mentioned technical problems, the technical scheme adopted in the present invention is as follows: a platinum catalyst for preparing low-carbon olefins by dehydrogenation of low-carbon alkanes comprises the following components in terms of catalyst weight percent:

a) At least one selected from ruthenium, rhodium, palladium, osmium, iridium or platinum among platinum group metals, calculated as 0.01 to 1.5% of the weight of the catalyst as a single substance;

b) At least one element or compound selected from Group IA or Group IIA of the Periodic Table of Elements, calculated as a single substance, is 0.05 to 35.0% of the weight of the catalyst;

c) Zinc ferrite carrier, where the carrier accounts for 63.5-94.9% of the weight of the catalyst.

In the above technical solution, the preferred composition of the carrier conforms to the formula: Zn _{x My} Fe ₂ O ₄ , where M is one of divalent or trivalent metal elements such as Ni, Cu, Co, Mn, Ce, Cr, Ge in the periodic table of elements Or several, and x+y=1, 0.5≤x<1, by weight percentage, including the following components:

a) Fe, calculated as a single substance, is 42.0 to 50.0% of the weight of the carrier;

b) Zn, calculated as a single substance, is 12.0 to 28.0% of the weight of the carrier;

c) M, calculated as a simple substance, is 0.1-15.0% of the weight of the carrier.

In the above technical scheme, the preferred range of the metal ion radius represented by M is between 0.060 and 0.080 nm; the carrier preferably has a spinel structure, and the preferred range of surface acidity of the carrier measured by the indicator method is lower than 0.4 mmol/g; M The /Zn ratio is between 0 and 1; the pore volume of the carrier is 0.08 to 0.8 cm ³ /g, and the specific surface area is 10 to 260 m ² /g.

The carrier can be made into different shapes according to the needs, such as cylindrical, spherical, flake, cylindrical, Raschig ring or honeycomb, etc., but cylindrical and spherical are better choices, and their effective diameter is 1 ~ 6mm, so that in industrial applications.

For solving above-mentioned technical problem two, the preparation method of catalyst comprises the following steps:

a) Configure the required amount of ferric nitrate hydrate, zinc nitrate hydrate and soluble salt of transition metal M into aqueous solution I, wherein M is selected from one of transition metal elements such as Ni, Cu, Co, Mn, Ce, Cr, Ge, etc. or several, the molar ratio of Fe:(Zn+M) is 1.5-2.5:1;

b) configuring an aqueous solution II of a soluble alkali with a mass percentage concentration range of 1 to 30%, and the soluble alkali is selected from at least one of sodium hydroxide, potassium hydroxide, ammonia water, and ammonium carbonate;

c) Add solution I to solution II at a precipitation temperature of 0-50°C, control the pH value to 7.0-10.5 under stirring conditions, filter and wash the precipitate at 50-150°C, and then dry it at 650-1000 ℃ roasting for 1 to 24 hours to obtain a composite zinc ferrite carrier;

d) Use the impregnation method to load the active components on the composite carrier, configure the required amount of chloroplatinate into an aqueous solution, impregnate the composite carrier for 1 to 48 hours, and dry to obtain a catalyst precursor; the catalyst precursor is roasted 1. After reduction, a catalyst for producing low-carbon alkanes by dehydrogenation of low-carbon alkanes is obtained.

In the above technical solution, the preferred range of precipitation temperature is 15-40° C.; the preferred range of pH value controlled under stirring conditions is 7.5-9.5.

A method for preparing low-carbon alkenes by dehydrogenating low-carbon alkanes, using propane and/or isobutane as raw materials, at a reaction temperature of 520-620°C, a reaction pressure of 0-0.4MPa, and an alkane mass space velocity of 0.1-8.0h ^-1 , under the condition that the volume ratio of H ₂ O/C _n H _2n+2 is 1-18, the raw material is contacted and reacted with the catalyst described in the technical solution to generate propylene and/or isobutene.

The present invention adopts the co-precipitation method to prepare composite zinc ferrite carrier, the transition metal composite iron oxide carrier containing magnesium, zinc and other metals is easy to form MFe ₂ O ₄ type spinel structure, on the carrier of this structure After a large number of oxygen ion holes and such lattice defects are generated, the interaction between the platinum metal particles and the alumina carrier is enhanced, which is beneficial to obtain a higher degree of dispersion and a more uniform distribution of the metal particles. However, ferric ions are easy to form strong Lewis acid centers, which leads to excessive activation of the reactants by the catalyst during the reaction process, low conversion rate, and easy to generate carbon deposits. The catalyst activity decreases and the selectivity also decreases. The acid center density (acidity) of the carrier is related to the structure and composition of the catalyst. In the present invention, the acidity of the zinc ferrite carrier is effectively reduced by adding a carrier modifying auxiliary agent. Metal ions with an ionic radius close to that of iron ions are used as the additives for carrier modification. The close ionic radius makes it easier for the additives to enter the oxide lattice, resulting in lattice deformation and unbalanced charge distribution, resulting in a decrease in acidity .

The dehydrogenation reaction of low-carbon alkanes is carried out on a continuous flow quartz tube reactor miniature catalytic reaction device. Product analysis adopts HP-5890 gas chromatograph (HP-AL/S capillary column, 50m * 0.53mm * 15μm; FID detector) the alkane in the dehydrogenation product, the content of alkene is analyzed on-line and the conversion rate of reaction, selectivity and yield. The catalyst obtained by this method is used under the conditions of 550°C, normal pressure, isobutane mass space velocity of 4.6 hours ^-1 , and H ₂ O/C ₄ H ₁₀ ratio of 8:1, and the initial conversion rate is higher than 45%. The stability is higher than 95%. After repeated regeneration, the metal particles can be kept below 3nm, and good technical effects have been achieved.

The prepared catalyst was measured by Hammett indicator titration method to measure the surface acid center density (total acidity of different acid strengths). The principle of this method is as follows:

B represents the basic Hammett indicator. When it is adsorbed on the surface of the catalyst, it interacts with the H+ on the surface to generate the corresponding conjugate acid BH+:

B+H+====BH+

A solid acid powder sample is suspended in a non-aqueous inert liquid and titrated with a base with the aid of an indicator. The base used for titration must be a stronger base than the indicator, usually n-butylamine with a pKa value of about +10. The added base first adsorbs on the most acidic sites and eventually displaces the indicator molecules from the solid. In this experiment, the standard n-butylamine-cyclohexane solution is used to titrate the solid acid to obtain the amount of acid. When an indicator is adsorbed on a solid acid and becomes an acid-type color, the titer of n-butylamine required to restore the indicator to a basic-type color is a measure of the number of acid centers on the surface of the solid acid. This method determines the total result of B acid and L acid.

The present invention will be further elaborated below by embodiment.

Description of drawings

Figure 1 is the XRD diffraction pattern of the composite zinc ferrite carrier (composite zinc ferrite spinel structure XRD pattern), its characteristic diffraction peaks 2θ=18.2±0.2°, 29.9±0.2°, 35.3±0.2°, 42.8± 0.2°, 53.1±0.2°, 56.6±0.2°, 62.2±0.2°.

detailed description

【Example 1】

Take 807.14g iron nitrate (Fe(NO ₃ ) ₃ 9H ₂ O), 247.62g zinc nitrate (Zn(NO ₃ ) ₂ 6H ₂ O), 48.29g nickel nitrate (Ni(NO ₃ ) ₂ 6H ₂ O) and dissolve in 2000ml of deionized water; at 25°C, under vigorous stirring, slowly add 5% wt. ammonia water dropwise to the mixed aqueous solution, control the pH value to about 7.5, and form a precipitate. Leave the precipitate at room temperature overnight, filter, wash, and Dry at 120°C, pulverize, sieve, and bake at 700°C for 16 hours to obtain a composite zinc ferrite carrier. XRD characterization shows that the support has a spinel structure, a pore volume of 0.29 cm ³ /g, and a specific surface area of 76 m ² /g. The carrier composition and acidity are shown in Table 1.

_The obtained support adopts the impregnation technique to load the platinum component, that is, at room temperature, 15.0 _g of the obtained support is impregnated with an aqueous solution ( ₁₀ ml ) for 24 hours (metal platinum loading 0.4%), then dried at 70°C, calcined at 540°C in air flow for 4 hours, then treated with water vapor at 540°C for 4.5 hours, and finally treated with dry air at 540°C for 1 hour. The resulting catalyst is designated as A.

The sample was reductively activated with hydrogen at 520°C for 120 minutes before the dehydrogenation reaction, and was used for isobutane dehydrogenation reaction.

[Example 2]

Take 809.6g iron nitrate (Fe(NO ₃ ) ₃ 9H ₂ O), 167.51g zinc nitrate (Zn(NO ₃ ) ₂ 6H ₂ O), 107.22g copper nitrate (Cu(NO ₃ ) ₂ 3H ₂ O) and dissolve in 2000ml of deionized water; at 25°C, under vigorous stirring, slowly add 10% ammonia water dropwise to the mixed aqueous solution to form a precipitate, control the pH value to about 7.8, leave the precipitate at room temperature overnight, filter, wash, in 100 ℃ drying, crushing, sieving, and calcining at 750 ℃ for 8 hours to obtain a composite zinc ferrite carrier. XRD characterization shows that the support has a spinel structure, a pore volume of 0.39 cm ³ /g, and a specific surface area of 86 m ² /g. The carrier composition and acidity are shown in Table 1.

_The obtained carrier adopts the impregnation technique to load the platinum component, that is, at room temperature, 15.0 _g of the obtained carrier is impregnated with an aqueous solution ( ₁₀ ml ) for 24 hours (metal platinum loading 0.4%), then dried at 60°C, calcined at 530°C in air flow for 3 hours, then treated with water vapor at 530°C for 4 hours, and finally treated with dry air at 530°C for 1 hour. The resulting catalyst is designated as B.

The sample was reductively activated with hydrogen at 500°C for 90 minutes before the dehydrogenation reaction, and was used for isobutane dehydrogenation reaction.

[Example 3]

Take 808.64g iron nitrate (Fe(NO ₃ ) ₃ 9H ₂ O), 154.65g zinc nitrate (Zn(NO ₃ ) ₂ 6H ₂ O), 139.32g cobalt nitrate (Co(NO ₃ ) ₂ 6H ₂ O) and dissolve in 2000ml of deionized water; at 26°C, under vigorous stirring, slowly add 20% ammonia water dropwise to the mixed aqueous solution to form a precipitate, control the pH value to about 8.8, leave the precipitate at room temperature overnight, filter, wash, in 100 ℃ drying, crushing, sieving, and calcining at 750 ℃ for 5 hours to obtain a composite zinc ferrite carrier. XRD characterization shows that the carrier has a spinel structure with a pore volume of 0.35 cm ³ /g and a specific surface area of 55 m ² /g. The carrier composition and acidity are shown in Table 1.

_The obtained carrier adopts the impregnation technique to load the platinum component, that is, at room temperature, 15.0 _g of the obtained carrier is impregnated with an aqueous solution ( ₁₀ ml ) for 24 hours (metal platinum loading 0.4%), then dried at 90°C, calcined at 530°C in air flow for 3 hours, then treated with water vapor at 530°C for 4 hours, and finally passed dry air at 530°C for 1 hour. The resulting catalyst is designated as C.

The sample was reductively activated with hydrogen at 500°C for 90 minutes before the dehydrogenation reaction, and was used for isobutane dehydrogenation reaction.

[Comparative Example 4]

Take 808.53g iron nitrate (Fe(NO ₃ ) ₃ 9H ₂ O), 276.15g zinc nitrate (Zn(NO ₃ ) ₂ 6H ₂ O), 20.21g cobalt nitrate (Co(NO ₃ ) ₂ 6H ₂ O) and dissolve in 2000ml of deionized water; under vigorous stirring at 26°C, slowly add 20% ammonia water dropwise to the mixed aqueous solution to form a precipitate, control the pH value to about 9.2, leave the precipitate at room temperature overnight, filter, wash, in 100 ℃ drying, crushing, sieving, and calcining at 750 ℃ for 6 hours to obtain a composite zinc ferrite carrier. XRD characterization shows that the support has a spinel structure, a pore volume of 0.58 cm ³ /g, and a specific surface area of 126 m ² /g. The carrier composition and acidity are shown in Table 1.

_The obtained carrier adopts the impregnation technique to load the platinum component, that is, at room temperature, 15.0 _g of the obtained carrier is used to impregnate an aqueous solution ( ₁₀ ml ) for 24 hours (metal platinum loading 0.4%), then dried at 80°C, calcined at 530°C in air flow for 3 hours, then treated with water vapor at 530°C for 4 hours, and finally treated with dry air at 530°C for 1 hour. The resulting catalyst is designated as D.

The sample was reductively activated with hydrogen at 520°C for 90 minutes before the dehydrogenation reaction, and was used for isobutane dehydrogenation reaction.

【Example 5】

Take 809.13g of iron nitrate (Fe(NO ₃ ) ₃ 9H ₂ O), 224.12g of zinc nitrate (Zn(NO ₃ ) ₂ 6H ₂ O), and 73.55g of cobalt nitrate (Co(NO ₃ ) ₂ 6H ₂ O) in 2000ml of deionized water; under vigorous stirring at 20°C, slowly add 20% ammonia water dropwise to the mixed aqueous solution to form a precipitate, control the pH value to about 9.5, filter the precipitate at room temperature overnight, wash, and Dry at 100°C, pulverize, sieve, and bake at 750°C for 4 hours to obtain a composite zinc ferrite carrier. XRD characterization shows that the support has a spinel structure, a pore volume of 0.46 cm ³ /g, and a specific surface area of 115 m ² /g. The carrier composition and acidity are shown in Table 1.

_The obtained carrier adopts the impregnation technique to load the platinum component, that is, at room temperature, 15.0 _g of the obtained carrier is used to impregnate an aqueous solution ( ₁₀ ml ) for 24 hours (metal platinum loading 0.4%), then dried at 90°C, calcined at 550°C in air flow for 4 hours, then treated with water vapor at 550°C for 4 hours, and finally treated with dry air at 550°C for 1 hour. The resulting catalyst is designated as E.

The sample was reductively activated with hydrogen at 500°C for 120 minutes before the dehydrogenation reaction, and was used for isobutane dehydrogenation reaction.

[Example 6]

Take 808.64g iron nitrate (Fe(NO ₃ ) ₃ 9H ₂ O), 196.02g zinc nitrate (Zn(NO ₃ ) ₂ 6H ₂ O), 85.56g manganese nitrate (Mn(NO ₃ ) ₂ 4H ₂ O) 2000ml of deionized water; at 20°C, under vigorous stirring, slowly add 22% ammonia water dropwise to the mixed aqueous solution to form a precipitate, control the pH value to about 10.2, filter the precipitate at room temperature overnight, wash, and Dry at 60°C, pulverize, sieve, and bake at 850°C for 3 hours to obtain a composite zinc ferrite carrier. XRD characterization shows that the support has a spinel structure, a pore volume of 0.16 cm ³ /g, and a specific surface area of 45 m ² /g. The carrier composition and acidity are shown in Table 1.

_The obtained carrier adopts the impregnation technique to load the platinum component, that is, at room temperature, 15.0 _g of the obtained carrier is impregnated with an aqueous solution ( ₁₀ ml ) for 24 hours (metal platinum loading 0.4%), then dried at 80°C, calcined at 530°C in air flow for 3 hours, then treated with water vapor at 530°C for 4 hours, and finally treated with dry air at 530°C for 1 hour. The resulting catalyst is designated as F.

The sample was reductively activated with hydrogen at 500°C for 90 minutes before the dehydrogenation reaction, and was used for isobutane dehydrogenation reaction.

[Example 7]

Take 807.56g iron nitrate (Fe(NO ₃ ) ₃ 9H ₂ O), 204.14g zinc nitrate (Zn(NO ₃ ) ₂ 6H ₂ O), 123.98g chromium nitrate (Cr(NO ₃ ) ₂ 4H ₂ O) and dissolve in 2000ml of deionized water; under vigorous stirring at 22°C, slowly add 22% ammonia water dropwise to the mixed aqueous solution to form a precipitate, control the pH value to about 8.5, filter the precipitate at room temperature overnight, wash, and Dry at 100°C, pulverize, sieve, and bake at 850°C for 3 hours to obtain a composite zinc ferrite carrier. XRD characterization shows that the carrier has a spinel structure, a pore volume of 0.28cm ³ /g, and a specific surface area of 76m ² /g. The carrier composition and acidity are shown in Table 1.

_The obtained carrier adopts the impregnation technique to load the platinum component, that is, at room temperature, 15.0 _g of the obtained carrier is impregnated with an aqueous solution ( ₁₀ ml ) for 24 hours (metal platinum loading 0.4%), then dried at 60°C, calcined at 530°C in air flow for 3 hours, then treated with water vapor at 530°C for 4 hours, and finally treated with dry air at 530°C for 1 hour. The resulting catalyst is designated G.

The sample was reductively activated with hydrogen at 500°C for 90 minutes before the dehydrogenation reaction, and was used for isobutane dehydrogenation reaction.

[Embodiment 8]

Get 808.41g ferric nitrate (Fe(NO ₃ ) ₃ 9H ₂ O), 183.69g zinc nitrate (Zn(NO ₃ ) ₂ 6H ₂ O), 38.76g germanium oxide (GeO ₂ ) and dissolve in 2000ml deionized water; ℃, under vigorous stirring, slowly add 15% ammonia water dropwise to the mixed aqueous solution to form a precipitate, control the pH value to about 10.0, leave the precipitate at room temperature overnight, filter, wash, dry at 120 ℃, pulverize, pass After sieving, it was calcined at 750° C. for 6 hours to obtain a composite zinc ferrite carrier. XRD characterization shows that the carrier has a spinel structure, a pore volume of 0.36 cm ³ /g, and a specific surface area of 94 m ² /g. The carrier composition and acidity are shown in Table 1.

_The obtained support adopts the impregnation technique to load the platinum component, that is, at room temperature, 15.0 _g of the obtained support is impregnated with an aqueous solution ( ₁₀ ml ) for 24 hours (metal platinum loading 0.4%), then dried at 80°C, calcined at 530°C in air flow for 3 hours, then treated with water vapor at 530°C for 4 hours, and finally treated with dry air at 530°C for 1 hour. The resulting catalyst is denoted as H.

The sample was reductively activated with hydrogen at 550°C for 90 minutes before the dehydrogenation reaction, and was used for isobutane dehydrogenation reaction.

[Example 9]

Take 808.10g iron nitrate (Fe(NO ₃ ) ₃ 9H ₂ O), 157.11g zinc nitrate (Zn(NO ₃ ) ₂ 6H ₂ O), 62.35g manganese nitrate (Mn(NO ₃ ) ₂ 4H ₂ O), 64.12 Dissolve g cobalt nitrate (Co(NO ₃ ) ₂ 6H ₂ O) in 2000ml deionized water; slowly add 15% ammonia water dropwise to the mixed aqueous solution at 26°C under vigorous stirring to form a precipitate, and control the pH value to about 9.8, the precipitate was left overnight at room temperature, filtered, washed, dried at 120°C, crushed, sieved, and calcined at 750°C for 8 hours to obtain a composite zinc ferrite carrier. XRD characterization shows that the carrier has a spinel structure with a pore volume of 0.33 cm ³ /g and a specific surface area of 114 m ² /g. The carrier composition and acidity are shown in Table 1.

_The obtained carrier adopts the impregnation technique to load the platinum component, that is, at room temperature, 15.0 _g of the obtained carrier is impregnated with an aqueous solution ( ₁₀ ml ) for 24 hours (metal platinum loading 0.4%), then dried at 90°C, calcined at 530°C in air flow for 3 hours, then treated with water vapor at 530°C for 4 hours, and finally passed dry air at 530°C for 1 hour. The resulting catalyst is designated as I.

The sample was reductively activated with hydrogen at 550°C for 90 minutes before the dehydrogenation reaction, and was used for isobutane dehydrogenation reaction.

【Example 10】

Take 808.33g of iron nitrate (Fe(NO ₃ ) ₃ 9H ₂ O), 182.15g of zinc nitrate (Zn(NO ₃ ) ₂ 6H ₂ O), and 93.24g of cadmium nitrate (Cd(NO ₃ ) ₂ ) in 2000ml of deionized In water; at 26°C, under vigorous stirring, slowly add 15% ammonia water dropwise to the mixed aqueous solution to form a precipitate, control the pH value to about 9.8, filter the precipitate at room temperature overnight, wash, and dry at 120°C Dry, pulverize, sieve, and bake at 750° C. for 8 hours to obtain a composite zinc ferrite carrier. XRD characterization shows that the carrier has a spinel structure, a pore volume of 0.37cm ³ /g, and a specific surface area of 106m ² /g. The carrier composition and acidity are shown in Table 1.

_The obtained carrier adopts the impregnation technique to load the platinum component, that is, at room temperature, 15.0 _g of the obtained carrier is impregnated with an aqueous solution ( ₁₀ ml ) for 24 hours (metal platinum loading 0.4%), then dried at 90°C, calcined at 560°C for 3 hours in air flow, then treated with water vapor at 560°C for 4 hours, and finally treated with dry air at 530°C for 1 hour. The resulting catalyst is designated as J.

The sample was reductively activated with hydrogen at 550°C for 90 minutes before the dehydrogenation reaction, and was used for isobutane dehydrogenation reaction.

[Example 11]

Take 810.16g of iron nitrate (Fe(NO ₃ ) ₃ 9H ₂ O), 99.84g of zinc nitrate (Zn(NO ₃ ) ₂ 6H ₂ O), 163.80g of copper nitrate (Cu(NO ₃ ) ₂ ) in 2000ml of deionized In water; at 26°C, under vigorous stirring, slowly add 15% ammonia water dropwise to the mixed aqueous solution to form a precipitate, control the pH value to about 9.8, filter the precipitate at room temperature overnight, wash, and dry at 120°C Dry, pulverize, sieve, and bake at 750° C. for 8 hours to obtain a composite zinc ferrite carrier. XRD characterization shows that the support has a spinel structure, a pore volume of 0.32 cm ³ /g, and a specific surface area of 112 m ² /g. The carrier composition and acidity are shown in Table 1.

_The obtained carrier adopts the impregnation technique to load the platinum component, that is, at room temperature, 15.0 _g of the obtained carrier is impregnated with an aqueous solution ( ₁₀ ml ) for 24 hours (metal platinum loading 0.4%), then dried at 90°C, calcined at 560°C for 3 hours in air flow, then treated with water vapor at 560°C for 4 hours, and finally treated with dry air at 530°C for 1 hour. The resulting catalyst is designated as K.

The sample was reductively activated with hydrogen at 550°C for 90 minutes before the dehydrogenation reaction, and was used for isobutane dehydrogenation reaction.

[Comparative Example 1]

The carrier and catalyst were prepared according to the method of Example 1. XRD characterization showed that the carrier had a typical spinel structure, and the different carrier precipitation process did not add modification aid components.

Table 1

After adding metal additives, the acidity of the catalyst surface decreased significantly.

[Examples 10-21]

The catalysts obtained in Examples 1-9 were evaluated at 550°C, normal pressure, isobutane mass space velocity 4.6 hours ⁻¹ , and H ₂ O/C ₃ H ₈ ratio of 8:1. The results are shown in Table 2.

Table 2*

The platinum tin catalyst prepared by ordinary zinc aluminate has higher acidity, more unstable performance, and obvious selectivity decay after 10 hours, and the performance and stability of the catalyst prepared by composite carrier are obviously improved.

[Example 20]

The catalysts were prepared and evaluated according to the steps and conditions in Example 1. Before the dehydrogenation reaction, the samples were reductively activated with hydrogen at 500° C. for 90 minutes and used for the isobutane dehydrogenation reaction. The catalyst was reacted for 10 hours at 550°C, normal pressure, isobutane mass space velocity of 4.6 hours ^-1 , and H ₂ O/C ₄ H ₁₀ ratio of 8:1, and then charcoal was fired at 500°C with 1% air for 60 minutes The catalyst was regenerated, and the initial performance of the catalyst after multiple regenerations is shown in Table 3.

table 3

Claims (10)

1. dehydrogenating low-carbon alkane prepares a low-carbon alkene platinum catalyst, in catalyst weight percent, comprises following component:

A) be selected from least one in ruthenium in platinum metal, rhodium, palladium, osmium, iridium or platinum, count 0.01 ~ 1.5% of catalyst weight with simple substance;

B) be selected from least one element in the periodic table of elements I A or II A race or its compound, count 0.05 ~ 35.0% of catalyst weight with simple substance;

C) zinc ferrite carrier, carrier accounts for 63.5 ~ 94.9% of catalyst weight.

2. dehydrogenating low-carbon alkane according to claim 1 prepares low-carbon alkene platinum catalyst, it is characterized in that carrier composition coincidence formula: Zn _xm _yfe ₂o ₄, wherein M is selected from one or more in the divalence such as transition metal Ni, Cu, Co, Mn, Ce, Cr or Ge or trivalent transition metal element, and x+y=1; By weight percentage, following component is comprised:

A) Fe, counts 42.0 ~ 50.0% of vehicle weight with simple substance;

B) Zn, counts 12.0 ~ 28.0% of vehicle weight with simple substance;

C) M, counts 0.1 ~ 15.0% of vehicle weight with simple substance.

3. dehydrogenating low-carbon alkane according to claim 2 prepares low-carbon alkene platinum catalyst, it is characterized in that 0.5≤x < 1.

4. dehydrogenating low-carbon alkane according to claim 2 prepares low-carbon alkene platinum catalyst, it is characterized in that metal ion radius that M represents is between 0.06 ~ 0.09nm.

5. dehydrogenating low-carbon alkane according to claim 2 prepares the catalyst carrier of low-carbon alkene, it is characterized in that the support acidity adopting indicator method to record is lower than 0.4mmol/g.

6. dehydrogenating low-carbon alkane according to claim 2 prepares low-carbon alkene platinum catalyst, it is characterized in that 0 < M/Zn≤1.

7. dehydrogenating low-carbon alkane according to claim 2 prepares low-carbon alkene platinum catalyst, it is characterized in that the pore volume 0.08 ~ 0.8cm of carrier ³/ g, specific area 10 ~ 260m ²/ g.

8. the dehydrogenating low-carbon alkane described in any one of claim 1 ~ 7 prepares the preparation method of low-carbon alkene platinum catalyst, comprises the following steps:

A) soluble-salt of the nitric hydrate iron of aequum, nitric hydrate zinc and transition metal M is configured to the aqueous solution I, wherein M is selected from one or more of the transition metals such as Ni, Cu, Co, Mn, Ce, Cr, Ge, Fe:(Zn+M) amount of substance ratio is 1.5 ~ 2.5:1;

B) aqueous solution II of the water soluble alkali of configuration quality percent concentration scope 1 ~ 30%, water soluble alkali is selected from least one of NaOH, potassium hydroxide, ammoniacal liquor, carbonic acid ammonia;

C) under the precipitation temperature of 0 ~ 50 DEG C, solution I is added in solution II, control ph 7.0 ~ 10.5 under stirring condition, after filtration, washing, this is deposited in 50 ~ 150 DEG C of oven dry, then 650 ~ 1000 DEG C of roastings 1 ~ 24 hour, compound zinc ferrite carrier is obtained.

D) adopt infusion process load active component on complex carrier, the chloroplatinate of aequum is configured to the aqueous solution, carrier flooded after 1 ~ 48 hour, after drying, obtains catalyst precarsor; Catalyst precarsor obtains dehydrogenating low-carbon alkane producing light olefins catalyst through roasting, reduction.

9. dehydrogenating low-carbon alkane according to claim 8 prepares the preparation method of low-carbon alkene platinum catalyst, and it is characterized in that the pH value of precipitation process is 7.5 ~ 9.5, precipitation temperature is at 10 ~ 45 DEG C.

10. dehydrogenating low-carbon alkane prepares a method for low-carbon alkene, adopts propane and/or iso-butane to be raw material, reaction temperature 520 ~ 620 DEG C, and reaction pressure 0 ~ 0.4MPa, alkane mass space velocity 0.1 ~ 8.0h ^-1, H ₂o/C _nh _2n+2volume ratio is under 1 ~ 18 condition, and described in raw material and any one of claim 1 ~ 7, catalyst exposure reacts and generates propylene and/or isobutene.